Satellite communication has several advantages, such as a wide coverage, low terrestrial interference, etc., and has been applied to many areas such as television broadcasting and wireless communication. Further, satellite signals can be received regardless of a position (e.g. a city without infrastructure, ocean or desert) of a receiver, as long as receiving antennas of the receiver are properly configured.
Please refer to FIG. 1, which is a schematic diagram of a satellite broadcasting system 10 according to an example of the prior art. The satellite broadcasting system 10 is suitable for a family, a building or a community. Each user in the family, the building or the community can receive satellite signals, such as Ku band (10.7-12.75 GHz) satellite signals, through a master antenna. In the satellite broadcasting system 10, a satellite receiver 100 receives the satellite signals, and down-converts frequency bands of the satellite signals to generate corresponding intermediate frequency (IF) signals with a frequency band of 0.95-2.15 GHz. Then, the IF signals are transmitted to a decoding device 102 (e.g. a set-top box) of each user, for decoding the IF signals. Thus, each user in the family, the building or the community can watch satellite broadcasting programs via various playback devices, such as a television and a computer.
In detail, a satellite receiver 100 comprises a satellite dish 110 and a low-noise block downconverter with feedhorn (LNBF) 120. Further, the LNBF 120 comprises an orthomode transducer (OMT) 122 and multiple low-noise block downconverters (LNBs) 124. After the LNBF 120 receives satellite signals via the satellite dish 110, the orthomode transducer 122 divides the satellite signals into vertical polarization signals and horizontal polarization signals which are outputted to the multiple low-noise block downconverters 124. Besides, the polarization signals can be further divided into high-band (HB) polarization signals and low-band (LB) polarization signals according to frequency bands of the polarization signals. That is, the polarization signals can be divided into LB horizontal polarization signals, HB horizontal polarization signals, LB vertical polarization signals and HB vertical polarization signals. After the low-noise block downconverter down-converts the frequency bands of the four types of the polarization signals to the intermediate frequency of 0.95-2.15 GHz, one of the four types of the polarization signals is outputted to the decoding device 102 of the user according to the choice of the user.
However, since choices of the users are usually different, a number of the low-noise block downconverters 124 should be proportional to a number of types of the polarization signals and a number of the users, to provide different IF signals to the users according to the choices of the users. For example, each user occupies four low-noise block downconverters 124 of the LNBF 120, such that the each user can freely choose one of the four types of the polarization signals. Therefore, when the number of the users is large, a large number of the low-noise block downconverters 124 must be installed in the LNBF 120 for serving the users. Both cost and power consumption of the satellite receiver 100 increase accordingly. Thus, how to raise the number of the polarization signals and the number of the users that a single low-noise block downconverter can serve is an important topic to be discussed.